Hurd, a relative newcomer to politics, turned the tables on Canseco, who beat him in a 2010 primary race on his way to winning a seat in Congress. Canseco lost two years later to Gallego, who now represents the sprawling 23rd congressional district that stretches from San Antonio to El Paso.

While Canseco was the better-known of the two GOP contenders, he also has endured unwelcome scrutiny by federal regulators looking into alleged campaign finance violations dating back to 2010. Canseco also struggled to raise money, some of which went to repay personal loans he had made to past congressional campaigns.

Both candidates ran on conservative platforms, but amid anti-incumbent sentiment among primary voters, Hurd was able to present himself as a fresh face without the taint of Washington.

Gallego, who has been able to stay above the fray, has raised more than $1.2 million for his reelection campaign, making him a formidable incumbent in what has become a swing district.